Atmospheric ammonia concentration measurements in Japanese laying hen buildings and modeling for emission inventory

Atmospheric ammonia (NH 3 ) from livestock contributes to PM2.5 formation and nitrogen loading in watersheds. Although chemical transport models often adopt the emission factor ( EF ) and monthly variation coefficient ( M f ) from European NH 3 emission inventories due to the limited availability of direct measurement data worldwide, their applicability to Asian countries remains unknown. In this study, we observed the spatial distributions and diurnal changes in NH 3 concentrations within windowless laying hen buildings during May–October of 2022 and 2023. The observed spatial distribution showed that the major drivers of monthly NH 3 emissions were air temperature and ventilation rate. Moreover, NH 3 concentrations changed depending on the number of days after manure removal according to the diurnal observations. A regression analysis was conducted using observed temperature, ventilation rate, and manure removal to develop a statistical model for estimating NH 3 emission rates based on ambient temperature data. Subsequently, model application to the different climatic conditions were performed by using the typical monthly mean air temperature from the surface weather databases at several major poultry production cities in Japan. The results demonstrated that the calculated EF in Japan varied substantially (0.11–0.52 kgNH 3 y −1 head −1 ) depending on air temperature, whereas that in the Netherlands remained near the lowest values. The summertime M f was higher in Japan than that in the Netherlands, suggesting differences in climate and manure management systems between Japan and Europe. To improve the accuracy of livestock emission inventories, further observations for NH 3 emission rate estimates are required for other sources, such as manure storage and land application.